1. Field of the Invention
The invention is related to the preparation of an ionic polymer composition comprising a protein and carbohydrate-containing vegetable material component, such as soy spent flakes, defatted soy flour, or soy protein concentrate. The composite composition is formed by incorporating soy spent flakes, defatted soy flour, or soy protein concentrate composition with ionic polymers. The composites have a significantly higher elastic modulus when compared with base polymer.
2. Description of the Prior Art
Soybean is composed of approximately 20% soybean oil, 8% hulls, and 72% defatted soy flour. Soybean also contains very little or no starch. Traditional approaches to the art of soybean processing involve appropriate preparation of the soybean prior to solvent extraction. After cracking of the beans and subsequent separation of the hull from the kernel portions, the cracked kernels are steam conditioned in large pressure cookers called bean conditioners that are located upstream from a flaking mill. The flaking mill functions to squeeze and impart a slight shear to the steam conditioned kernels resulting in the formation of a thin meal flake having a diameter of around 0.50 inch and a thickness of about 10-16 mils. After the meal has been flaked, the traditional approach is to route the flaked meal to a further heat processing step or directly to extraction processes. This further heat processing step may occur within a jacketed screw press conveyor with steam being injected into the working section of the conveyor. The flakes are there steam treated and are mechanically worked. The meal exiting the die orifices of the screw conveyor can best be described as including dust-like particles that are combined in the form of a pellet or pellets. After the flaked, steam treated pellets exit the second heating step, they are sent to extraction processes including extractors, desolventizer-toasters, dryer-cooler, meal grinding and meal storage stations. During these processes, the meal is mixed with a solvent, such as hexane, which dissolves the soybean oil. The soybean oil-solvent mixture is then separated from the meal particles. The desired soybean oil may then be isolated from the solvent solution by conventional techniques such as distillation, etc. The meal itself is desolventized, dried and then ground and stored prior to use.
After the hulls are removed and soybean oil is extracted, the remaining material is called defatted soy flour, which is composed of soy protein and soy carbohydrate. (Protein Resources and Technology, 1978) The defatted soy flour usually contains more than 50 percent soy protein. The defatted soy flour can further be processed to separate soy protein from soy carbohydrate. The separated soy protein usually contains more than 90 percent protein and is called soy protein isolate. Soy carbohydrate contains a soluble fraction called whey and an insoluble fraction called spent flakes. The defatted soy flour can be further subjected to acidic treatment to separate the whey from the protein and insoluble carbohydrate. The remaining material after whey removal is called soy protein concentrate containing more than 70 percent protein. The protein and insoluble carbohydrate is then further separated by alkali treatment. An alternative process is to treat defatted soy flour in alkali condition to separate the insoluble carbohydrate first and then separate the soy protein from the whey in acidic condition. If the alkali process is used to separate the spent flakes (mostly soy carbohydrate), the composition of spent flake is approximately 12% cellulose, 17% pectin, 14% protein, and 53% insoluble polysaccharide. It is clear that the composition of soy carbohydrate is very different from starch that contains mostly amylose and amylopectin. The defatted soy flour, soy spent flake, and soy protein concentrate used in this invention can be defined as the mixture of soy protein and soy carbohydrate that contains 15-90% soy carbohydrate.
Protein, in general, has been suggested as a component in rubber latex. For example, U.S. Pat. No. 2,056,958 discloses a flexible floor covering composition containing casein (milk protein) and rubber latex. U.S. Pat. No. 2,127,298 shows a composition consisting of protein, starch, and resinous matter for applications such as abrasive wheels and paint formulations. This patent also discloses a composition containing soya bean meal, lime, sodium fluoride, aluminum stearate, an oleo-resin, isopropyl alcohol, and dispersed rubber. However, the patent does not teach the use of soya bean meal in ionic polymers such as carboxylic acid or sulfonic acid modified rubber for modulus reinforcement. U.S. Pat. No. 2,931,845 teaches the composition of rubber-protein-glyoxal for modulus reinforcement. U.S. Pat. No. 3,113,605 teaches using a mixture of protein and carbohydrate in rubber tires to modify frictional properties, such as anti-skid resistance. U.S. Pat. No. 5,446,078 discloses using dry reactive melt blending of protein with polymers containing non-ionic maleic anhydride to form covalent bonds. The patent does not teach the use of a combination of soy protein and soy carbohydrate to achieve synergistic reinforcement effects in a polymer matrix. The reaction of maleic anhydride with active hydrogen functional groups from protein can only occur in the dry state, and the alkali neutralized maleic anhydride groups can not be used because the salt of maleic anhydride is not reactive. The patent also fails to teach the formation of intimate ionic complexes in aqueous phase with neutralized carboxylic acid functional groups, where the interaction between the reinforcing phase and the polymer matrix is an ionic interaction instead of covalent bonding. U.S. Pat. No. 6,632,925 teaches using plant protein and a compatibilizer in polylactide composites. However, polylactide is not an ionic polymer because it does not contain ionic functional groups along the polymer backbone for it to be water dispersible. Therefore, polylactide cannot be used to form a complex with soy products in alkali water solution and is not suitable as a polymer matrix in the present invention. U.S. Pat. Nos. 4,812,550 and 4,607,089 teach the grafting of various reactive monomers onto protein or modified protein with a free-radical initiator. These patents do not teach the formation of non-reactive ionic complex to enhance composite modulus. U.S. Pat. No. 6,291,559 B1 teaches the use of modified or non-modified soy protein and polyacrylate to thicken paper coating dispersions. There is no teaching herein of using a combination of soy protein and soy carbohydrate to achieve synergistic reinforcement effects in a polymer matrix. U.S. Pat. No. 4,185,146 teaches composite formation by reacting diisocyanate with non-ionic polyalkylene ether polyol and solid soybean derivatives in a dry state since the reaction cannot occur in the presence of water. This patent does not show the formation of an ionic complex in water phase. None of these references teach the use of soy spent flakes, defatted soy flour, or soy protein concentrate in the structural reinforcement of ionic polymer materials.